Method for metal wetting liners



April 7, 1970 J. a. WALKER ET AL 3,5 ,1

METHOD FOR METAL WETTING LINERS Filed April 22, 1965 2 Sheets-Sheet 1 SOURCE OF COMPRESSED AIR INVENTORS James 5 [Ml/kw; tr 1% mmd .5, fl/m/a April 7, 1970 J. B. WALKER ET AL METHOD FOR METAL WETTING LINERS Filed April 22, 1965 2 Sheets-Sheet 2 INVENTORS v James bf Mz/rrex; 6/ BY 1% zm'za b, fZ/m/a ATTORNEY United States Patent 3,505,103 METHOD FOR METAL WE'ITING LINERS James E. Walker, Almont, and Raymond S. Amala, Oak Park, Mich., assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Apr. 22, 1965, Ser. No. 450,043 Int. Cl. C23c 1/08 US. Cl. 117114 13 Claims ABSTRACT OF THE DISCLOSURE A method of wetting a ferrous metal article with a nonferrous metal by immersing the article into a bath of molten non-ferrous metal followed by the production of high frequency resonant vibrations in a surface located in the bath adjacent the peripheral surface of the article so that sonic wave energy emanating from the surface is concentrated in the area of the peripheral surface.

This invention concerns a method for wetting a ferrous metal article with molten aluminum and more particularly a method that accelerates the aluminum wetting of a ferrous metal brake liner by using sonic vibrations.

Current production methods of wetting ferrous metal brake liners with molten aluminum under static immersion conditions require a relatively long time to obtain uniform wetting. Therefore, in order to achieve a reasonable production output, large volumes of molten aluminum are utilized so that a number of the liners can be immersed simultaneously. In addition, conveyors and fixtures must be used to carry and immerse the parts in the large baths of metal and, as should be apparent, this type of production operation results in high maintenance costs and requires large floor areas. Another difiiculty is that the conveyor systems and fixtures are subject to erosion and oidation resulting in impurities, alloying elements, and other metallic contaminates adversely effecting the wetting characteristics of the bath and therefore unless strict control of the metal bath composition is provided, acceptable wetting cannot be realized.

One of the objects of the present invention is to provide an improved wetting process.

Another object is the provision of a method which efficiently utilizes vibratory energy to bond a thin layer of molten aluminum to the outer surface of a ferrous metal brake liner.

A further object is the provision of a method which utilizes sonic standing wave vibratory energy for wetting with molten aluminum a ferrous metal ring-shaped liner which has the peripheral surface thereof formed with a multiplicity of protrusions and interstices.

The above objects and others are accomplished in accordance with the present invention by a method which concentrates vibratory energy within certain areas of an aluminum bath so as to realize optimum wetting of the liner. Stated broadly, in the preferred form of the method a ferrous metal brake liner is immersed into a bath of molten aluminum after which a radiator surface is positioned in the molten aluminum and subjected to high frequency resonant vibration so as to direct sonic waves into localized areas adjacent the periphery of the brake liner. The vibratory energy developed in the molten aluminum causes intense cavitation to occur in the molten aluminum resulting in improved metal bonding between the ferrous metal surface of the brake liner and the aluminum. One form of sonic vibratory apparatus successfully utilized for practicing the method comprises an elongated bar, one end of which supports a pair of counter-rotating air-driven vibrators. A fiexural member is carried by the other end of the bar and is coupled to a fiat annular surface which constitutes the radiator surface. A source of compressed air is provided for driving the vibrators at a resonant standing wave frequency of the fiexural member with the outer edge of the latter located at an antinode point so that the radiator surface is subjected to high amplitude vibration.

A more complete understanding of the subject invention can be derived from the following detailed description taken in conjunction with the drawings in which:

FIGURE 1 is an elevation view illustrating the vibratory apparatus made in accordance with the invention;

FIGURE 2 is a vieW taken on line 22 of FIGURE 1, and

FIGURE 3 shows a modified version of the lower end of the vibratory apparatus illustrated in FIGURE 1.

Referring now to the drawings and more specifically FIGURES 1 and 2 thereof, a vibratory apparatus 10 made in accordance with the invention is shown supported by a plate 12 which in turn rests on the upper end of a container 14. The container 14 is filled to a predetermined level with a molten aluminum and has the floor portion thereof formed with a boss 15 so as to suitably support and locate a ring-shaped brake liner 16 in a predetermined position preparatory to the wetting thereof. The container is made from a refractory material, such as high alumina or silicon carbide, so it can withstand the high temperatures of the molten aluminum.

The vibratory apparatus 10 comprises an elongated cylindrical force transmitting bar 18, which at its upper end is connected with a vibration generating means 20 that includes a pair of air-driven vibrators 22 and 24. The vibration generating means 20 is of a type shown in detail in FIGURES 1 and 4 of copending United States Patent application Ser. No. 355,569, entitled Sonic Method and Apparatus For Wetting Metals, filed Mar. 30, 1964 and assigned to the assignee of this invention. Reference is made to the aforesaid patent application for a complete understanding of the type of vibration generating means utilized with this invention; however, for present purposes, it will suffice to say that the vibrators 22 and 24 each have a cylindrical working chamber in which a cylindrical roller 26 is freely located and adapted to orbit thereabout. A plurality of jets are tangentially located about the working chamber and are adapted to direct high velocity streams of compressed air that impinge against the peripheral surface of the roller so as to drive the latter about the working camber and thereby produce a rotating force vector which acts against the support housing of the vibrator. Suitable passage means are provided in the bar to direct air to the jets for driving the rollers of the respective vibrators in opposite directions and thereby cause all forces other than those acting along the longitudinal axis of the bar 18 to be canceled. Thus, in effect, the Vibration generating means 20 incorporated with this invention produces a reciprocating force that acts along the longitudinal axis of the bar 18.

The lower end of the bar 18 extends through an opening 26 in the plate 12 and is centrally connected to a disk-shaped member 28 which is bolted adjacent the edge thereof to the upper end of an annular coupling member 30 that terminates at its lower end with a planar radiator surface 32. The member 30 is made of cast iron; however, in cases where increased durability is desired, it can be made of a ceramic material. The bar 18 is supported on the plate 12 through an isolator assembly 34 that includes a mounting plate 36. A plurality of circumferentially and equally spaced studs 38 extend downwardly from the mounting plate 36 and have the threaded ends thereof accommodated by appropriate openings 40 formed in the support plate 12 and connected to the latter by nuts 42. A coil spring 44- encircles each stud and has the upper end contacting the mounting plate 36 while the lower end is seated in a well 46 found in the surface of the support plate 12. As should be apparent, the springs 44 serve to isolate the vibratory apparatus from the supporting structure and thereby preclude any loss of vibratory energy thereto during the operation of the apparatus.

Immediately above the mounting plate 36 an air manifold collar 48 is locked to the bar 18 and includes an air inlet port 50 which receives compressed air from a suitable source indicated by the numeral 52 via an air conduit 54. An air control valve 55 is interposed in the conduit 54 and serves to regulate the air flow to the vibration generating means 20. In this particular form of the apparatus, a cylindrical baffie 56 is attached to the support plate 12 by four equally spaced rods 58, 60, 62 and 64 as best seen in FIGURE 2. The rods are rigidly connected at their lower ends to the baflle 56 and slidably supported at their upper ends by the support plate 12. As will be more fully understood as the description of the invention proceeds, the baffle can take other forms, the purpose thereof primarily being to act as a means for confining and reflecting vibratory energy emanating from the radiator surface 32.

In practicing the invention, the container 14 is first filled with molten aluminum to a level which assures that the upper end of the liner is submerged below the upper surface 65 of the bath but still allows sufiicient room for partial submersion of the coupling member as seen in FIGURE 1. As aforementioned, suitable means (not shown) are utilized for maintaining the aluminum in a molten state and such means can be a channel type induction furnace, an open hearth furnace, or a gas-fired crucible furnace. The aluminum provided in the container 14 can either be a pure aluminum or an aluminum alloy.

Whi e maintaining the aluminum in a molten state, the brake liner 16 is immersed into the bath of aluminum and located, as shown, with its inner diameter surrounding the guide boss 15. This procedure is normally followed when the liner is made from steel; however, when made from cast iron, the peripheral serface of the liner should be cleaned preparatory to immersion so as to assure a good metallurgical bond between the dissimilar metals. There are various methods of cleaning the peripheral surface of the cast iron liner and some cleaning treatments which have been found acceptable include sandblasting, an electrolytic salt bath treatment, or mechanically cutting a thin layer of metal from the outer surface of the liner. Once the outer surface of the cast iron liner is cleaned, it is then dipped into the bath of aluminum and located in a manner as described above.

The vibratory apparatus 10 is then energized by opening the valve 55 so as to direct compressed air from the source 52 to the vibration generating means 20. Sufiicient air is supplied to the vibrators 22 and 24 to enable the latter to direct force impulses through the bar 18 to the member 28 at a frequency which is in the range of the resonant frequency of the member 28 so that the latter vibrates in a standing wave form as illustrated in FIG- URE 1. During standing wave vibration the points ofv minimized vibration amplitude are termed nodes, and the points of maximized vibration amplitude are termed antinodes. When the member 28 is subjected to this form of vibration, it does not vibrate bodily or as a whole but elastically in a 'flexural wave form. As seen in FIGURE 1, during resonant standing wave vibration the center and the outer edges of the member 2-8 are located at antinode points with a nodal circle existing therebetween and passing through points N and N. Thus, the coupling member 30 is located on an antinodal circle and therefore experiences increased deflection as a result of resonant operation.

It will be understood that during production operation the vibratory apparatus 10 and the container 14 can be incorporated into a press type machine. In other words,

the container would be supported by the stationary or lower platen while the vibratory apparatus would be suitably mounted to the movable or upper platen coaxial with the boss 15. Thus, once the vibratory apparatus 10 is brought up to its operating frequency and the press is closed, the radiator surface 32 is immersed into the molten aluminum to a point slightly above the liner 16. It will be noted that the batlle 56 will then contact the floor of the container and be located concentric with and adjacent to the outer surface of the liner. Thus, a certain amount of the molten aluminum will be confined within the enclosure created by the baffle 56 and the vibratory energy emanating from the radiator surface 32 can now be concentrated in the area between the bafile and the peripheral surface of the liner. This permits the baffle to act as a reflector of the sonic waves generated by the radiator surface 32 and serves to confine the vibratory energy to an area adjacent to the periphery of the liner and thereby produce increased cavitation which results in a wetting of the brake liner.

In one test run of the method and vibratory apparatus described above, extremely good wetting was obtained on the peripheral surface of a cast iron brake liner which was approximately three inches in height, had an inner diameter of twelve inches and an outer diameter of twelve and one-half inches. An aluminum alloy was utilized for accomplishing the wetting and was composed of 9.5% silicon, 0.5% magnesium and a balance of pure aluminum. The bath of aluminum was maintained at a temperature between 1400 and 1450 F. Prior to wetting, the liner was cleaned by mechanically cutting a thin layer of metal from the entire outer surface of the liner. The vibratory apparatus utilized in this particular test consisted of a bar 18 having a length of 42.75 inches and a major diameter of 3.0 inches. The bar was connected to a disk-shaped member 28 which had a diameter of 14 inches, a center thickness of 1.16 inches, and tapered down to an edge thickness of 0.50 inch. The vibrators 22 and 24 were of a type that were capable of generating 1,000 pounds of force at 1,000 cycles per second. The coupling member 30 had an over-all height of 3 inches, an outer diameter of 14.75 inches with an inner diameter of 11.25 inches.

During the wetting process in the above-mentioned test run the radiator surface 32 of the coupling member was located approximately 0.25 inch from the upper edge of the liner. It was found that so long as this distance was in a range between 0.25 and 0.75 inch, good wetting was obtained. The inner wall of the baflle 56 was located a distance between 0.50 and 1.0 inch from the peripheral surface of the brake liner. During this particular test mm, the disk-shaped member achieved resonant standing wave movement at approximately 800 cycles per second and had a peak-to-peak amplitude of approximately 0.009 inch at the antinode points. Acceleration levels of the radiator surface 32 were measured in air and found to be in the area of 300 gs and complete wetting of the peripheral surface of the brake liner was obtained in several seconds. As should be apparent, after the brake liner was wetted, as explained above, the vibratory apparatus was raised out of the aluminum bath followed by removal of the brake liner for further processing. A new brake liner can then be placed in the aluminum bath and the process repeated.

FIGURE 3 shows a modified form of the coupling member which, in this case, is indicated by the numeral 66. In this form of the invention, the coupling member 66 includes a laterally extending flange 68 having a radiator surface 70 integrally formed with a depending skirt 72 which is adapted to surround the brake liner 16 and act as a reflector in the manner of the baffle 56 incorporated with the apparatus shown in FIGURE 1. Except for this diiference, the vibratory apparatus is identical to that previously described and operated in a similar manner for achieving wetting of the brake liner.

It will be noted that parts corresponding to those incorporated with the apparatus of FIGURE 1 are identified by corresponding numerals but primed.

In both of the embodiments of the vibratory apparatus it will be noted that the coupling member has a radiator surface which extends laterally beyond the outer diameter of the brake liner. In addition, in both cases some form of baflle or reflecting means is positioned adjacent to the periphery of the brake liner during the wetting operation so that molten aluminum is confined in a small area next to the peripheral surface of the brake liner. Thus, the sonic waves emitted from the radiator surface of the coupling member are concentrated in localized portions of the bath. It is believed that primarily because of this particular type of arrangement optimum wetting can be obtained. Another important feature of this invention is the resonant operation of the disk-shaped member 28. As alluded to hereinbefore, during resonant operation maximum vibration amplitude is realized in the elastic member accompanied by high levels of acceleration.

It has been found that the above-described method and apparatus are particularly suited for wetting ferrous metal brake liners that have the outer peripheral surface thereof formed with a multiplicity of irregular metallic protrusions and interstices. One method for forming this type of roughened surface can be found in the patent to Myers 2,623,809. A good wetting of a brake liner of this type cannot be obtained under static immersion conditions due to surface tension characteristics of the materials. However, with this invention the irregular surface of the liner can be readily infiltrated and wetted because the induced cavitation dislodges any foreign matter including occluded gases from the interface.

Although the invention has been described as utilizing aluminum for wetting cast iron and steel, it has also been found that other non-ferrous metals, such as zinc, can also be used in this process for obtaining good wetting of the liner.

We claim:

1. A method of wetting the peripheral surface of a ferrous metal ring-shaped brake liner with a non-ferrous metal, comprising the steps of maintaining a bath of nonferrous metal in a molten state, immersing the brake liner into said bath of molten metal, maintaining a reflector surface closely adjacent to said peripheral surface so as to provide an annular space therebetween, placing an annular coupling ring having an outer diameter greater than the 'brake liner into said bath slightly above and coaxial with the brake liner, subjecting said coupling ring to high frequency resonant vibrations, and concentrating the vibratory energy emanating from said coupling ring in the space between said reflector surface and said peripheral surface.

2. A method of wetting the peripheral surface of a ringshaped cast iron brake liner with aluminum, comprising the steps of maintaining a bath of aluminum in a molten state, cleaning the peripheral surface of said liner, immersing the liner into said bath of molten aluminum, producing high frequency resonant vibrations in a flexural member, coupling said flexural member to a sonic wave radiator surface, maintaining a reflector surface closely adjacent to said peripheral surface so as to provide an annular space therebetween, and immersing said radiator surface in said bath in a position so that sonic wave energy emanating from said radiator surface is concentrated in the area between said reflector surface and said peripheral surface of the liner.

3. The method of claim 2 wherein said peripheral surface is cleaned by a sandblasting treatment.

4. The method of claim 2 wherein said peripheral surface is cleaned by a salt bath treatment.

5. A method of wetting the peripheral surface of a ringshaped cast iron brake liner with aluminum, comprising the steps of maintaining a bath of aluminum in a molten state, mechanically removing a thin layer of metal from the peripheral surface of said liner, immersing the brake liner into said bath of molten aluminum, producing high frequency resonant vibrations in a flexural member, coupling said flexural member to a sonic wave radiator surface, maintaining a reflector surface closely adjacent to said peripheral surface so as to provide an annular space therebetween, and immersing said radiator surface in said bath in a position so that vibratory energy emanating from said radiator surface is concentrated in the space between said reflector surface and said peripheral surface of the liner.

6. A method of wetting the peripheral surface of a cast iron brake liner with aluminum, comprising the steps of maintaining a bath of aluminum in a molten state, cleaning the peripheral surface of said liner, immersing the brake liner into said bath of molten aluminum, maintaining a reflector surface closely adjacent to said peripheral surface so as to provide an annular space therebetween, producing high frequency resonant vibrations in a flexural member, coupling said flexural member to a sonic wave radiator surface, and immersing said radiator surface in said bath whereby a plane passing through said surface is substantially perpendicular to said peripheral surface and in a position so that vibratory energy emanating from said radiator surface is concentrated in the space between said reflector surface and said peripheral surface of the liner.

7. A method of wetting the peripheral surface of a cast iron brake liner with aluminum, comprising the steps of maintaining a bath of aluminum in a molten state, cleaning the peripheral surface of said liner, immersing the brake liner into said bath of molten aluminum, maintaining said brake liner in a stationary position, maintaining a reflector surface closely adjacent to said peripheral surface so as to provide an annular space therebetween, producing high frequency resonant vibrations in a flexural member, coupling said flexural member to a sonic wave radiator surface, and immersing said radiator surface in said bath whereby a portion of said surface extends laterally beyond the peripheral surface of the liner so that vibratory energy emanating from said radiator surface is concentrated in the space between said reflector surface and said peripheral surface of the liner.

8. A method of wetting the peripheral surface of a cast iron brake liner with aluminum, comprising the steps of maintaining a bath of aluminum in a molten state, cleaning the peripheral surface of said liner, immersing the brake liner into said bath of molten aluminum, maintain ing said brake liner in a stationary position, maintaining a reflector surface closely adjacent to said peripheral surface so as to provide an annular space therebetween, producing high frequency resonant standing wave vibrations in a flexural member, coupling the antinodal point of said flexural member to a sonic wave radiator surface, and immersing said radiator surface in said bath in a position so that sonic wave energy emanating from said radiator surface is concentrated in the space between said reflector surface and said peripheral surface of the liner.

9. A method of wetting the peripheral surface of a cast iron ring-shaped brake liner with aluminum, comprising the steps of maintaining a bath of aluminum in a molten state, cleaning the peripheral surface of said brake liner, immersing the brake liner into said bath of molten aluminum so that the axis of the liner is substantially normal to the plane of the upper surface of said bath, maintaining said brake liner in a stationary position, maintaining a reflector surface closely adjacent to said peripheral surface so. as to provide an annular space therebetween, placing an annular coupling ring having an outer diameter greater than the brake liner into said bath slightly above and coaxial With the brake liner, subjecting said coupling ring to high frequency resonant vibrations, and concentrating the vibratory energy emanating from said coupling ring in the space between said reflector surface and said peripheral surface.

10. A method of wetting the peripheral surface of a cast iron ring-shaped brake liner with aluminum, comprising the steps of maintaining a bath of aluminum in a molten state, cleaning the peripheral surface of said brake liner, immersing the brake liner inio a bath of molten aluminum, maintaining said brake liner in a stationary position, maintaining a reflector surface closely adjacent to said peripheral surface so as to provide an annular space therebetween, placing an annular coupling ring having an outer diameter greater than the brake liner into said bath slightly above and coaxial with the brake liner, subjecting said coupling ring to high frequency resonant standing Wave vibrations, and concentrating the vibratory energy emanating from said coupling ring in the space between said reflector surface and said peripheral surface.

11. A method of making a bi-metallic brake liner, comprising the steps of providing a ferrous metal ring-shaped liner having the peripheral surface thereof formed with a multiplicity of protrusions and interstices, maintaining a bath of aluminum in a molten state, immersing said liner into said bath of molten aluminum, maintaining a reflector surface adjacent said peripheral surface, producing high frequency resonant vibrations in a fiexural member having a radiator surface, and locating said radiator surface in said bath so as to create an intense cavitation field in the area located between the reflector surface and said peripheral surface.

12. The method of claim 11 wherein a portion of said radiator surface extends laterally beyond the peripheral surface of the liner.

13. The method of claim 11 wherein said radiator surface is positioned in a plane substantially normal to the axis of said liner.

References Cited UNITED STATES PATENTS 3,305,384 2/1967 Kenderi 1171 14 XR 3,410,534 11/1968 Wyczalek 259-72 2,616,820 11/1952 Bourgeaux.

2,657,668 11/1953 Maier.

2,970,933 2/1961 Barera et al.

3,082,119 3/1963 Harris.

3,084,020 4/1963 Loosli.

3,194,681 7/1965 Nicholson et al.

ALFRED L. LEAVIT T, Primary Examiner W. F. CYRON, Assistant Examiner 

